In recent years, attempts have been made to use as actuators various forms of driving devices provided with a shape memory alloy (hereinafter referred to as “SMA”). The SMA is typically represented by a titanium-nickel alloy. It has a property that even if the SMA is deformed at a temperature lower than the temperature called “transformation point”, it goes back to the original state by martensite transformation when it is heated above that temperature. Normally, the SMA is made in the form of a string, and is expanded and contracted along the length by electricity-powered heat control, whereby the SMA can be used as an actuator.
Such an SMA has a wire size as small as several tens of microns. This allows downsizing of an apparatus equipped with the SMA actuator. Thus, studies have been made to mount the SMA on various types of apparatuses.
Incidentally, generally, such a string-like SMA is supported on a base member, which is provided on a frame or casing, through a fixing member to fix both ends thereof, and is extended to a driven member. Further, there is provided is on or around the fixing member an electrical connection terminal to which a lead wire or a flexible printed circuit board for applying electricity to the SMA is to be connected.
For example, according to one of the techniques known in the conventional art, an SMA is pinch-held to be fixed by pressure contact in a pinching section formed by bending a plate-formed member. A lead wire for supplying electricity to the SMA is inserted between an annular washer member provided at the sandwiching section and the base member, and is secured by a screw (Unexamined Japanese Patent Application Publication No. 2006-189036).
In another known technique, an SMA is fixed by press-fitting together with a ball or wedge into the hole provided in a base member, and a lead wire for supplying electricity to the SMA is soldered onto the connection terminal arranged in the vicinity of the hole of the base member (Unexamined Japanese Patent Application Publication No. 2002-98911).
However, the technique disclosed in the Unexamined Japanese Patent Application Publication No. 2006-189036 provides a so-called lag plate where the washer member connected with the lead wire and the sandwiching section where the SMA is pinch-held to be fixed by pressure contact are laterally integrated. This structure requires a large two-dimensional space and may cause difficulties in downsizing the device.
In the technique disclosed in the Unexamined Japanese Patent Application Publication No. 2002-98911, the hole of the base member to which the SMA is fixed and the connection terminal to which the lead wire is soldered are located close to each other. This structure may cause the SMA performance to be adversely affected by heat transmission resulting from soldering work.